Nudibranchs | The Colorful World of Sea Slugs (49 images)

A nudibranch is a member of a suborder of soft-bodied, marine gastropod mollusks.

The word 'nudibranch' comes from the Latin nudus, naked, and the Greek brankhia, gills. They are noted for their often extraordinary colors and striking forms.
Nudibranchs are often casually called 'sea slug', but many sea slugs belong to different taxonomic groups not related to nudibranchs.
Nudibranchs vary in adult size from about 1-60 cm and have cephalic (head) tentacles sensitive...more »

A nudibranch is a member of a suborder of soft-bodied, marine gastropod mollusks.

The word 'nudibranch' comes from the Latin nudus, naked, and the Greek brankhia, gills. They are noted for their often extraordinary colors and striking forms.
Nudibranchs are often casually called 'sea slug', but many sea slugs belong to different taxonomic groups not related to nudibranchs.
Nudibranchs vary in adult size from about 1-60 cm and have cephalic (head) tentacles sensitive to touch, taste, and smell. The club-shaped rhinophores detect odors.

Some nudibranchs feed on hydroids and store the hydroids' nematocysts (stinging cells) in their dorsal body wall, the cerata. These stolen nematocysts wander through the alimentary tract of the nudibranch and are brought to specific placements on the creature's hind body via intestinal protuberances. Nudibranchs themselves are, through an unknown mechanism, protected from these nematocysts.
Other nudibranchs use a variety of chemical defenses to aid in protection, but it is not necessary for the strategy to be lethal in order to be effective: some successful toxins induce hypotension in a predator, allowing the nudibranch to escape consumption while its attacker is incapacitated.
Some sponge-eating nudibranchs concentrate the toxins from their prey sponge in their bodies, rendering themselves toxic to predators. Certain species are even able to produce their own chemicals without dietary influence.
Yet another method of protection is the release of a caustic acid from the skin.

Nudibranchs are hermaphroditic, i.e. they simultaneously possess fully developed reproductive organs of both sexes. However it still 'takes two to tango', as self-fertilization is only known in one species.
They lay their eggs in every size, color and shape from an oviduct located on the right side of their body, most often in a counter-clockwise spiral. Some of the brightly colored eggs are caustic or toxic to ward off potential predators.« less